Retrograde ductal administration of the adenovirus-mediated NDRG2 gene leads to improved sialaden hypofunction in estrogen-deficient rats.

One of the most common oral manifestations of menopause is xerostomia. Oral dryness can profoundly affect quality of life and interfere with basic daily functions, such as chewing, deglutition, and speaking. Although the feeling of oral dryness can be ameliorated after estrogen supplementation, the side effects of estrogen greatly restrict its application. We previously found that N-myc downstream-regulated gene 2 (NDRG2) is involved in estrogen-mediated ion and fluid transport in a cell-based model. In the present study, we used an ovariectomized rat model to mimic xerostomia in menopausal women and constructed two adenovirus vectors bearing NDRG2 to validate their therapeutic potential. Ovariectomized rats exhibited severe sialaden hypofunction, including decreased saliva secretion and ion reabsorption as well as increased water intake. Immunohistochemistry revealed that the expression of NDRG2 and Na(+) reabsorption-related Na(+)/K(+)-ATPase and epithelial sodium channels (EnaC) decreased in ovariectomized rat salivary glands. We further showed that the localized delivery of NDRG2 improved the dysfunction of Na(+) and Cl(-) reabsorption. In addition, the saliva flow rate and water drinking recovered to normal. This study elucidates the mechanism of estrogen deficiency-mediated xerostomia or sialaden hypofunction and provides a promising strategy for therapeutic intervention.

N-myc downstream-regulated gene 2, a novel estrogen-targeted gene, is involved in the regulation of Na+/K+-ATPase.

Na(+)/K(+)-ATPase, a plasma membrane protein abundantly expressed in epithelial tissues, has been identified and linked to numerous biological events, including ion transport and reabsorption. In Na(+)/K(+)-ATPase, the ß-subunit plays a fundamental role in the structural integrity and functional maturation of holoenzyme. Estrogens are important circulating hormones that can regulate Na(+)/K(+)-ATPase abundance and activity; however, the specific molecules participating in this process are largely unknown. Here, we characterize that N-myc downstream-regulated gene 2 (NDRG2) is an estrogen up-regulated gene. 17ß-Estradiol binds with estrogen receptor ß but not estrogen receptor α to up-regulate NDRG2 expression via transcriptional activation. We also find that NDRG2 interacts with the ß1-subunit of Na(+)/K(+)-ATPase and stabilizes the ß1-subunit by inhibiting its ubiquitination and degradation. NDRG2-induced prolongation of the ß1-subunit protein half-life is accompanied by a similar increase in Na(+)/K(+)-ATPase-mediated Na(+) transport and Na(+) current in epithelial cells. In addition, NDRG2 silencing largely attenuates the accumulation of ß1-subunit regulated by 17ß-estradiol. Our results demonstrate that estrogen/NDRG2/Na(+)/K(+)-ATPase ß1 pathway is important in promoting Na(+)/K(+)-ATPase activity and suggest this novel pathway might have substantial roles in ion transport, fluid balance, and homeostasis.

Research on a novel rigid internal fixation system.

PURPOSE: The purpose of the present study was to evaluate the efficiency of fixation with a novel (bulge core type system) rigid internal fixation system. MATERIALS AND METHODS: Mandibular linear fractures were created artificially in dogs and fixed using a bulge core type system or a miniplate system in vitro. A 3-point load cell was used to contrast the fixation strength of the 2 systems in vitro. Histologic sections were used to analyze the healing of mandibular linear fractures and to contrast the efficiency of fixation of the 2 systems in vivo. Tetracycline-fluorescein staining technology was used to evaluate the bone healing speed in the mandibular fracture lines during bone healing. RESULTS: In vitro, the 3-point load cell showed that the fixation strength of the bulge core type system was greater than that of the miniplate system (P < .05). In vivo, the histologic sections and tetracycline-fluorescein staining showed that greater and quicker bony healing occurred using the bulge core type system (P < .05) and that the efficiency of fixation of the 2 systems was similar. CONCLUSION: Our results have shown that the bulge core type system can provide sufficient strength for mandibular linear fracture healing.

BZW1, a novel proliferation regulator that promotes growth of salivary muocepodermoid carcinoma.

Mucoepidermoid carcinoma (MEC) is the most common primary malignancy in the salivary glands; however, its oncogenesis is poorly understood. Here, we show that the homo sapiens basic leucine zipper and W2 domains 1 (BZW1 or BZAP45) is a critical factor in the regulation of MEC growth. Firstly, BZW1 was highly expressed in MEC tissues and cells, determined by quantitative real time polymerase chain reaction. Higher levels of BZW1 proteins were detected in MEC tissues, particularly in high-grade MEC, by immunohistochemistry. Furthermore, down-regulation of BZW1 expression by infection with BZW1-specific RNAi-expressing lentivirus inhibited Mc3 cell proliferation and colony formation in vitro. In addition, down-regulation of BZW1 expression arrested Mc3 cell cycling at the G(0)/G(1) phase and mitigated Mc3 cell migration and invasiveness in vitro, determined by wound healing and transwell invasion assays. Importantly, down-regulation of BZW1 expression significantly reduced the tumorigenicity of Mc3 cells in vivo, evidenced by the slow progression of small tumors induced by BZW1-specific RNAi expressing Mc3 cells. Apparently, BZW1 is a novel factor, promoting the growth of MEC cells. Our findings may provide a base for design of new strategy for diagnosis and therapy for human MEC.

ClC chloride channels in tooth germ and odontoblast-like MDPC-23 cells.

OBJECTIVE: To detect expression of ClC chloride channel mRNA in tooth germ and odontoblasts, and explore the affect of chloride channel function on cell proliferation and cell cycle. DESIGN: We extracted total RNA of tooth germ from newborn C57BL mice and mouse odontoblast-like cells (MDPC-23), then detected mRNA expression of chloride channel genes Clcn1-7 with RT-PCR. We used chloride channel blocker 5-nitro-2-(3- phenylpropylamino)benzoic acid (NPPB) to interfere with chloride channel function of MDPC-23 cells. Cell proliferation rate and cell cycle were detected with MTT assay and flow cytometry, respectively. Student's t-test was used to determine statistical significance between control and treatment groups. RESULTS: The mRNA of Clcn1-7 chloride channel genes was expressed in tooth germ of newborn mice. Clcn3, Clcn5 and Clcn7 mRNAs were expressed in MDPC-23 cells. NPPB slowed down the proliferation rate of MDPC-23 cells from day 2 to day 4 (P<0.01), and also changed the proportion of cell cycle phase. Comparing to the control, the proportion of G2/M phase cells reduced from 3.93+/-2.62% to 0.54+/-0.25% (P<0.05). The ratio of G1/G2 increased from 1.86+/-0.01 to 1.95+/-0.02 (P<0.05). CONCLUSIONS: There is abundant chloride channel gene expression in tooth germ. Some of these chloride channels may regulate tooth development through effects on cell proliferation and cell cycle signal pathway.